Workers at Italy's Meridiana Airline protest on May 12 against proposed layoffs. Europe's sluggish economy is fueling widespread dissatisfaction with the 28-nation European Union. Much of the eurozone — the 19 EU states that use the euro currency — is just emerging from the 2007–09 global recession. (Getty Images/Corbis/Stefano Montesi)

As the 28-nation European Union approaches its 60th anniversary, it is struggling to hang together in the midst of numerous challenges, including sluggish economies, a migration crisis and rising populism. Founded in the ashes of World War II, the EU sought to end ruinous national rivalries and forge an organization in which Europeans would work together to build a prosperous future. The EU's supporters say the Union has largely fulfilled these goals but that its success has led to an irony: Expansion from the original six member states has opened up new divisions between the wealthier north and the poorer south and between those states favoring a stronger central authority and those wanting power returned to national capitals. Britain's vote to exit the EU — dubbed Brexit — has raised further questions about the Union's viability. For now, many analysts agree, steps toward greater integration appear impossible, although the EU might be able to press ahead with plans for closer cooperation among members' militaries after Britain leaves.